Help me understand what is happening with my batteries, I'm lost.

[pops106]

I have got 10 x 55ah batteries I have posted a few times about them, they are all second hand so no idea of age or remaining capacity and I originally had a few problems with them going out of balance so I bought an active balancer and it has worked pretty well but spotted one in particular was getting more current then the others. There is a LED on the balancers to show which way the flow is going.

So I decided to pull it apart and bought a capacity tester so I could get the best 8 of the 10 back in 4s2p for 48v.

Tested B1 10amp draw to 12v and got 23.38ah
Tested B2 10amp draw to 12v and got 9.39ah
Tested B3 10amp draw to 12v and got 9.03ah
Tested B4 10amp draw to 12v and got 10.65ah

Ran a battery repair on B1 and B2 and got

B1 23.33ah
B2 6.01ah

So declared B2 dead, B3 and B4 probably as bad

So I took B3 and tested C20 discharge rate 2.75amp to 10.5v to get total wh which was 411wh out of potentially 660wh battery so roughly worked that out to be 36ah capacity out of a 55ah battery so not dead but not great but also obviously not less than half of the good B1 battery.

Decided quickest way to weed out the bad was a new test C10 5.5amp down to 12.4v

B1 10.27ah (known good from previous test)
B10 9.99ah (marking as good)
B2 6.56ah (known bad)
B3 1ah (know bad but was similar to B2 in other tests)

So comparing B1 to B2 over the different tests;

Test 1 B1 is 149% better then B2
Test 2 B1 is 288% better then B2
Test 3 B1 is 57% better then B2

During the test;

B10 (good) started 13.6v ish dropped to 12.8v ish once loaded then worked down slowly to 12.4v
B1 (good) started 13.6v ish dropped to 12.42v once loaded then recovered to 12.62v after a few mins then slowly down to 12.4v
B2 (bad) started 13.6v ish dropped to only 13.2v once loaded and slowly dropped to 12.4v
B3 (bad) started 13.2v ish dropped to 12.45v once loaded and dropped to 12.4v

Nothing seems to be consistent.

I feel like if I charge again redo the tests especially anything but B1 the results will be different.

Batteries are Lucas LSLC55-12 says on the front VRLA, doesn't mention AGM but most websites do so is it potentially charging with a standard lead acid charger I think it goes to 14.6v 5.9amp constant current then constant voltage down to .1a

It is not as inconsistent as this when it is on my SCC's but I am not obviously watching it for hours on end.

 

[RCinFLA]

Would have to see the voltage verses time for the test and a little use history on batteries. Regular use employed float and absorb voltages.

Three possible reasons:

Sulfation if not recharged regularly and left for weeks at partial state of charge - loss of capacity due negative plate blockage
Oxidation of positive plate grid structure due to long float charging. - high impedance voltage drop with load.
Loss of electrolyte water, due to overchargng, sustained high float voltage. capacity and impedance.

I assume your 'repair' cycle is equilization which should not be done on VRLA. They will vent causing loss of electrolyte water.

 

[pops106]

Would have to see the voltage verses time for the test and a little use history on batteries. Regular use employed float and absorb voltages.

Three possible reasons:

Sulfation if not recharged regularly and left for weeks at partial state of charge - loss of capacity due negative plate blockage
Oxidation of positive plate grid structure due to long float charging. - high impedance voltage drop with load.
Loss of electrolyte water, due to overchargng, sustained high float voltage. capacity and impedance.

I assume your 'repair' cycle is equilization which should not be done on VRLA. They will vent causing loss of electrolyte water.

I'm planning to measure the voltages today during a charge to see exactly what the charger is doing so at least I have that info.

The repair mode literally just says pulse repair which isn't exactly helpful but will measure voltages for that as well but I have never heard/smelt them gas/vent which I have in the past with other batteries.

EDIT> Measured and it basically charges slowly with a pulse so it measures like 13.01 > 13.02 > 13.01 > 13.02 > 13.02 > 13.03v

Thank you for the breakdown of the causes.

• Sulfation if not recharged regularly and left for weeks at partial state of charge - loss of capacity due negative plate blockage
  • I have the chargers kick in on a night and they don't quite have enough time to fully charge before solar kicks in and the chargers switch off but it doesn't take much sun for them to charge at least up to voltage so I would say it is rare they don't get charged.
• Oxidation of positive plate grid structure due to long float charging. - high impedance voltage drop with load.
  • They are in use everyday on my solar so are never left floating for a long period
• Loss of electrolyte water, due to overchargng, sustained high float voltage. capacity and impedance.
  • Very possible on some of the batteries for short periods when one has ramped up vs the others but I stop it, I have pulled the total voltage down on the charge controller to stop this happening but it means some of the batteries wont hit 14.6v for example but that is what I am trying to solve.

Of course this is only what I know since I have had the batteries.

Any ideas on the inconsistency of the results from testing ?

Something I have noticed is some of the batteries after a charge but still left on the charger seem to consume a tiny amount of watts from the charger when others don't.



I am measuring using a smart plug.

The first one is a desulfer at the beginning, soft start 3.1amp then 5.9amp bulk then tail off, test, top up and finish at just before 12:00 after that it sits at 4.2w which is the same as a charger not connected to the battery.

Second about 12:30 same as above but after finish it jumps to 9w and slowly slowly tails off too 1w with a few spikes before I disconnect for the next battery, I am guessing this is float but again it is different for different batteries.